The hollow fibre apparatus of the prior art, which can be used as an artificial kidney or an artificial lung and in which the fluid outside the fibres circulates from one sealing element to the other, are essentially apparatuses in which the blood circulates inside fibres which are essentially rectilinear and held together in a bundle inside a casing which is generally cylindrical in form. This requires that the sealing elements through which the fibres pass be cut with the greatest of care in order to ensure the passage of blood inside the fibres; in fact, the slightest surface roughnesses which may result from cutting of the sealing elements and the fibres, which can also lead to a flattening of fibre ends, will normally result in local coagulation of the blood. Such coagulation often spreads during the course of a haemodialysis session. Additionally, good haemocompatibility properties need to be possessed by the material of which the fibres and the sealing elements are made. Also, such must have good mechanical properties in order that cutting operations may be carried out to leave a smooth surface. In the apparatuses of the prior art in which blood is passed through the inside of hollow fibres, the inner wall of the fibres must possess a surface condition which is such that blood haemolysis or coagulation does not take place.
The apparatuses of the prior art are essentially designed for circulation of the blood inside the fibres, and means for introduction and/or withdrawal of fluid which is circulated outside the fibres are normally situated on the casing section surrounding the hollow fibres. If such apparatuses are used with blood circulating outside the fibres, regions will be poorly irrigated at least in the part which is diametrically opposite to the point of entry of blood in the chamber. Risks of coagulation will be significant in these parts.
One aim of the present invention is therefore to provide an apparatus which does not have the disadvantages of the apparatuses of the prior art and in which a fluid, especially blood, can be circulated about the outer surfaces of the hollow fibres, without risk of poor irrigation. An advantage of the apparatus according to the present invention resides in the fact that it suffices to cut the fibres without needs to achieve a perfect surface condition of their ends or of the sealing elements, since blood when circulated outside of the fibres would not come into contact with the cut surfaces. Another advantage of the apparatus of the present invention is that is makes it possible to use hollow fibres which may have a certain roughness or unevenness of the inside surface.
A further advantage of the apparatus according to the present invention resides also in the ease of cleaning of the circuit for the fluid which circulates outside the fibres.